Isotropic liquid crystals or optical isotropic liquid crystals refer to the liquid crystals having a birefringence of zero when no electric field is applied thereto; for example, blue phase (BP) liquid crystals or isotropic phase (cleaning phase) liquid crystals (which have a higher temperature than the blue phase liquid crystals). The blue phase is a liquid crystal phase which exists within a narrow range of temperature (in 1° C. to 2° C.) between the temperature of cholesteric phase (CH) and isotropic phase. Therefore, applications of the blue phase liquid crystals are very limited. However, when 5 wt % to 20 wt % of polymers are added into the blue phase liquid crystals, the resulting liquid crystals can have a wider range of temperature, and are called polymer-stabilized blue phase liquid crystals (PSBPLC). This polymer-stabilizing method can also be used with isotropic phase liquid crystals, and are called polymer-stabilized isotropic phase liquid crystals (PSIPLC).
The blue phase liquid crystals and isotropic liquid crystals are optical isotropic when no electric field is applied thereto. Therefore, they do not need to be orientated like the traditional nematic liquid crystals. Optical isotropic material may be transformed to be anisotropic by an electric field. In other words, the birefringence (Δn) can be induced by an electric field. In addition, they have fast response time of less than 1 ms and a high contrast ratio. Thus, the orientation layer may not be required. Therefore, blue phase liquid crystals and isotropic liquid crystals become an emerging display technology.
However, although the workable temperature of the blue phase liquid crystals or the isotropic liquid crystal can be broadened by the polymer-stabilized technique, the displays still surfer from problems related to the operating voltage and hysteresis.
Therefore, optical isotropic liquid crystals with a lower operating voltage and less hysteresis are desired.